Why is Riven balanced around Animation Cancelling?

So I've decided to learn and attempt to master Riven through lots of practice. I do not believe she is by any means "broken" or "OP", but I chose her because she will push me to get better mechanically and learn how to properly animation cancel.

that said, already in my very limited experience with her, she is basically awful if you do NOT play her well with great timing on the animation cancels. usually champions who have a high skill cap, also can be somewhat useful if you play smart on them while you are still learning them. Lee Sin, Leblanc, etc. all come to mind. Riven on the other hand just feels like I am basically going to get shit on while i take the hundreds of games to master her.

Before the hate comes in, I want to be clear I do SUCK with riven because I am learning her and I do not expect to be stomping or even winning most of my games while I learn a new champion. This post is more about how Riven feels damage output/usefulness wise while you are not at a high level on her.

I Feel like because she CAN animation cancel and do insane burst combos in the blink of an eye, she will always be awful to anyone else who is not at that level. It just feels shitty to be honest. Can anyone answer me why she is balanced around such an intense level of mechanical skill? Is it just so she doesn't get out of control by the players who do master her?